Methods and apparatus for reducing hydrogen permeation from lithographic tool

ABSTRACT

An apparatus for reducing hydrogen permeation of a mask is provided when generating extreme ultraviolet (EUV) radiation. The apparatus includes a mask stage configured to hold the mask, a hydrogen dispensing nozzle configured to eject hydrogen below the mask, and a trajectory correcting assembly. The trajectory correcting assembly includes a correcting nozzle and a gas flow detector. The correcting nozzle is configured to dispense at least one flow adjusting gas to adjust a trajectory of the hydrogen away from the mask to reduce hydrogen permeation at an edge of the mask. The gas flow detector is configured to measure a variation of an airflow of the hydrogen adjusted by the at least one flow adjusting gas.

BACKGROUND

Functional density, i.e., number of interconnected devices per chip, ofsemiconductor integrated circuits (ICs) has increased over the years.This increase in functional density has been achieved by reducing thesize of individual devices on the chip. Semiconductor manufacturingtechniques such as photolithography needed to continue this decreasingtrend in size of devices are met by decreasing the wavelength of lightused in photolithography to extreme ultraviolet (EUV) wavelengths.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of an EUV lithography system, in accordancewith embodiments of the present disclosure.

FIG. 2 is a schematic diagram of a detail of an extreme ultravioletlithography tool relating to embodiments of the present disclosure.

FIG. 3 schematically illustrates a mask holding mechanism relating tosome embodiments of the present disclosure.

FIG. 4A illustrates a cross-sectional schematic view of a reticleholder.

FIG. 4B illustrates a plan view of the reticle holder.

FIG. 4C illustrates other plan views of hydrogen permeation at an edgeof the reticle.

FIGS. 5A and 5B are schematic views of the trajectory of the hydrogenand a trajectory correcting assembly according to embodiments of thedisclosure.

FIG. 5C illustrates a plurality of nozzles according to embodiments ofthe disclosure.

FIGS. 5D and 5E are schematic views of trajectory of the hydrogen and anexhaust nozzle according to embodiments of the disclosure.

FIG. 5F is a schematic view of a plurality of nozzles and a plurality ofexhaust nozzles according to embodiments of the disclosure.

FIG. 6 shows a schematic of a feedback control system for controlling aprocess according to some embodiments of the present disclosure.

FIG. 7A illustrates a collect-analyze-tune (CAT) operation in accordancewith some embodiments of the present disclosure.

FIGS. 7B and 7C illustrate block diagrams of non-limiting examples of anairflow pattern recognition system in accordance with one or moreembodiments described herein.

FIG. 8 shows a flow chart of a method of controlling a feedback systemof an extreme ultraviolet (EUV) radiation source according to anembodiment of the disclosure.

FIGS. 9A and 9B illustrate a controller in accordance with someembodiments of the disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus/device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein may likewise be interpreted accordingly. In addition, theterm “made of” may mean either “comprising” or “consisting of.” In thepresent disclosure, a phrase “one of A, B and C” means “A, B and/or C”(A, B, C, A and B, A and C, B and C, or A, B and C), and does not meanone element from A, one element from B and one element from C, unlessotherwise described.

The present disclosure is generally related to extreme ultraviolet (EUV)lithography system and methods. More particularly, it is related toapparatuses and methods for cleaning a reticle holder used to secure areticle in an EUVL exposure tool.

Because gas molecules absorb EUV light, the lithography system for theEUV lithography patterning is maintained in a vacuum or a low pressureenvironment to avoid EUV intensity loss and to prevent adverse effectsof ionized gases on the wafer on which EUVL is being performed, thevarious layers present on the wafer, and the optical components used inthe EUVL exposure tool. Therefore, an electrostatic reticle holder isused in EUVL systems to secure reticles. However, because of the forcewith which the reticle holder secures the reticle, contaminant particleson the reticle holder can damage the reticle holder as well as thereticle. Moreover, such contaminant particles on the reticle holder cancause minute distortions in the reticle surface, resulting in distortionin the pattern being produced on the wafer.

To suppress particles or contaminant from accumulating on the reticle orthe reticle holder, a gas flow, such as a hydrogen gas flow, is providedto the reticle holder. During an extreme ultraviolet (EUV) lithographyprocess, however, the hydrogen flow drifts towards a surface of thereticle due to its light molecular weight. The drifted hydrogenaccumulates/deposits at an edge of the reticle, permeating into thespace between the reticle and a covering film. This hydrogen permeation(also called a “blister problem”) onto the reticle results in bubbles atthe edge of the reticle and causes the covering film to peel off.Undesirable particles generated by the peeled-off film can interferewith the further processing steps. Therefore, it is beneficial toprevent the undesirable particles caused by hydrogen permeation as apart of the lithographic process.

One of the objectives of the present disclosure is directed to cleaningthe reticle holder while reducing down time of the exposure tool andreducing damage to reticle holder and the reticle.

FIG. 1 is a schematic view of an EUV lithography system with a laserproduced plasma (LPP) based EUV radiation source, in accordance withsome embodiments of the present disclosure. The EUV lithography systemincludes an EUV radiation source 100 to generate EUV radiation, anexposure tool 200, such as a scanner, and an excitation laser source300. As shown in FIG. 1 , in some embodiments, the EUV radiation source100 and the exposure tool 200 are installed on a main floor MF of aclean room, while the excitation laser source 300 is installed in a basefloor BF located under the main floor. Each of the EUV radiation source100 and the exposure tool 200 are placed over pedestal plates PP1 andPP2 via dampers DP1 and DP2, respectively. The EUV radiation source 100and the exposure tool 200 are coupled to each other by a couplingmechanism, which may include a focusing unit.

The lithography system is an EUV lithography system designed to expose aresist layer by EUV light (also interchangeably referred to herein asEUV radiation). The resist layer is a material sensitive to the EUVlight. The EUV lithography system employs the EUV radiation source 100to generate EUV light, such as EUV light having a wavelength in a rangefrom about 1 nm to about 100 nm. In one particular example, the EUVradiation source 100 generates EUV light with a wavelength centered atabout 13.5 nm.

The exposure tool 200 includes various reflective optical components,such as convex/concave/flat mirrors, a mask holding mechanism includinga mask stage, and wafer holding mechanism. The exposure tool 200 furtherincludes an exposure chamber 205 that encloses all of the opticalcomponents, mask holding mechanism and wafer holding mechanism of theexposure tool 200. The exposure chamber 205 provides a vacuumenvironment for the exposure tool 200 to avoid loss of intensity of theEUV radiation because of absorption from gases.

FIG. 2 is a simplified schematic diagram of a detail of an extremeultraviolet lithography tool according to an embodiment of thedisclosure showing the exposure of the photoresist coated substrate 410with a patterned beam of EUV light. The exposure device 200 is anintegrated circuit lithography tool such as a stepper, scanner, step andscan system, direct write system, device using a contact and/orproximity mask, etc. The exposure device 200 is provided with one ormore optics 250 a, 250 b, for example, to illuminate a patterning optic250, such as a reticle, with a beam of EUV light, to produce a patternedbeam, and one or more reduction projection optics 250 c, 250 d, forprojecting the patterned beam onto the substrate 410. A mechanicalassembly (not shown) may be provided for generating a controlledrelative movement between the substrate 410 and patterning optic 250. Asfurther shown in FIG. 2 , the EUVL tool includes an EUV light source 100including an EUV light radiator ZE emitting EUV light in a chamber 105that is reflected by a collector 110 along a path into the exposuredevice 200 to irradiate the substrate 410.

As used herein, the term “optic” is meant to be broadly construed toinclude, and not necessarily be limited to, one or more components whichreflect and/or transmit and/or operate on incident light, and includes,but is not limited to, one or more lenses, windows, filters, wedges,prisms, grisms, gradings, transmission fibers, etalons, diffusers,homogenizers, detectors and other instrument components, apertures,axicons and mirrors including multi-layer mirrors, near-normal incidencemirrors, grazing incidence mirrors, specular reflectors, diffusereflectors and combinations thereof. Moreover, unless otherwisespecified, the term “optic”, as used herein, is not meant to be limitedto components which operate solely within one or more specificwavelength range(s), such as at the EUV output light wavelength, theirradiation laser wavelength, a wavelength suitable for metrology or anyother specific wavelength.

In various embodiments of the present disclosure, the photoresist coatedsubstrate 410 is a semiconductor wafer, such as a silicon wafer or othertype of wafer to be patterned.

FIG. 3 schematically illustrates a mask holding mechanism in accordancewith an embodiment of the present disclosure. The following descriptionrefers to FIG. 2 and FIG. 3 . The EUV radiation EUV generated by the EUVradiation source 100 is guided by the reflective optical components ontoa mask 250 secured on the mask stage 210. In some embodiments, the maskstage 210 includes an electrostatic reticle holder 220 (interchangeablyreferred to herein as electrostatic chuck or e-chuck) to secure the mask250.

In the present disclosure, the terms mask, photomask, and reticle areused interchangeably. In the present embodiment, the reticle 250 is areflective mask. In an embodiment, the reticle 250 includes a substrate252 formed of a suitable material, such as a low thermal expansionmaterial or fused quartz. In various embodiments, the substrate materialincludes TiO₂ doped SiO₂, or other suitable materials with low thermalexpansion. The mask 250 includes multiple reflective multiple layers(ML) (not shown) deposited on the substrate 252. The ML includes aplurality of film pairs, such as molybdenum-silicon (Mo/Si) film pairs(e.g., a layer of molybdenum above or below a layer of silicon in eachfilm pair). Alternatively, the ML may include molybdenum-beryllium(Mo/Be) film pairs, or other suitable materials that are configurable tohighly reflect the EUV light. The mask 250 may further include a cappinglayer (not shown), such as ruthenium (Ru), disposed on the ML forprotection. The mask 250 further includes an absorption layer 255, suchas a tantalum boron nitride (TaBN) layer, deposited over the ML. Theabsorption layer 255 is patterned to define a layer of an integratedcircuit (IC). Alternatively, another reflective layer may be depositedover the ML and is patterned to define a layer of an integrated circuit,thereby forming an EUV phase shift mask.

FIG. 4A illustrates a cross-sectional schematic view of a reticle holder220. FIG. 4B illustrates a plan view of the reticle holder 220. FIG. 4Cillustrates other plan views of hydrogen permeation at an edge 950 ofthe reticle 250. The reticle 250 and electrostatic chuck 221 arepositioned such that radiation EUV supplied from the EUV radiationsource is in focus when it arrives at the surface of the semiconductorworkpiece. A reticle mini environment (RME) provides contamination andenvironmental control in semiconductor manufacturing operation by anisolation of equipment and processes. The RME is an enclosure configuredto separate an operating personnel from the equipment, therebymaintaining a locally controlled process environments. The RME allows anaccess to the equipment for loading and maintenance. In someembodiments, a dummy reticle mini environment (RME) 940 may beconstructed without any internal components in the structure of the RME.As the dummy RME allows an access to the equipment for loading andmaintenance, in the present configuration, a Y-nozzle 920 is mountedwithin the dummy reticle mini environment (RME) 940, and ejects hydrogen930 along the y-axis. The y-axis is perpendicular to the x-axis of thereticle, an axis along the motion by the hydrogen and perpendicular tothe z-axis, which is the axis substantially normal to the surface of thereticle.

A number of sensors 130 may be disposed on a bottom surface of theelectrostatic chuck 221. The sensors 130 are positioned to be proximateto the reticle 250 during operation, for example near the edge of thereticle 250. The sensors 130 may be fixedly mounted on the electrostaticchuck 221 and may be used to evaluate and/or optimize imagingperformance of the EUV illumination tool. One or more sensors 130 mayinclude a lower plate that is transparent to radiation, such asradiation in the EUV wavelength, or may include a pattern of transparentportions and opaque portions. The sensor 130 may include an opticalelement, such as a fiber optic plate or micro lens array, which issuitable to direct or focus the received radiation to a transducer. Thetransducer may be a device to convert radiation to an electric signal,such as a photodiode, a CCD camera, or a CMOS camera. The output of thetransducer may be used to control, calibrate, or optimize the operationof the EUV illumination tool.

In some embodiments, the sensors 130 a may be transmission image sensors(TIS). A TIS sensor is used to measure the position of a projectedaerial image of a mask pattern on the reticle 250. The projected imagemay be a line pattern with a line having comparable wavelength to thewavelength of the radiation. The measurement of the TIS sensors 130 amay be used to measure the position of the mask with respect to thereticle stage in six degrees of freedom, e.g., three degrees of freedomin translation and three degrees of freedom in rotation. Additionally,magnification and scaling of the projected pattern may also be measuredby the TIS sensors 130 a. The TIS sensors 130 a are capable of measuringpattern positions, influences of illumination settings, such as sigma,numerical aperture of lens. The TIS sensors 130 a may be used to alignthe reticle 250 with the substrate, focus the EUV radiation to a targetregion on the substrate, measure performance of the EUV illuminationtool, and/or measure optical properties, such as pupil shape, coma,spherical aberration, astigmatism, and field curvature.

In some embodiments, the sensor 130 c may be a spot sensor configured tomeasure a dose of EUV radiation at the substrate level. The measured EUVradiation by the spot sensor 130 c at the substrate level can be used tocalculate the EUV radiation absorbed by mirrors in the path of the EUVradiation 108 for compensating the effects of EUV radiation loss, whichmay improve optical performance of the EUV illumination tool.

In some embodiments, the sensor 130 d is an integrated lensinterferometer at scanner (ILIAS). An ILIAS sensor is an interferometricwave front measurement device that performs static measurement on lensaberrations up to a high order. The ILIAS sensor 130 d may be used tomeasure wavefront errors in the EUV radiation 108.

It should be noted that other sensors may be included in the reticlestage to achieve target functions. Different sensors may be combinedinto one sensor to achieve multiple functions. For example, a TIS sensormay be combined to with an ILIAS sensor to measure both projected aerialimages and wavefront errors.

As shown in FIG. 5A, a Y-nozzle 920 is a nozzle configured to eject gasalong a y-axis and perpendicular to an x-axis and a z-axis. During theEUV lithography process, the hydrogen flow 930 ejected by the Y-nozzle920 along the y-axis drifts towards a surface of the reticle due to itslight molecular weight. Because the hydrogen is lighter than air, itrises in a vertical direction relative to the air. The drifted hydrogen932 accumulates/deposits at the edge 950 of the reticle 250, permeatinginto the space between the reticle and a covering film 952. Thishydrogen permeation (also called a “blister problem”) onto the reticle250 results in bubbles at the edge of the reticle and causes peeling offof the covering film. Undesirable particles generated by the peeled-offfilm can interfere with further processing steps. Therefore it isbeneficial to prevent undesirable particles caused by the hydrogenpermeation as a part of the lithographic process.

As shown in FIG. 5B, a correcting nozzle 1010 of a trajectory correctingassembly 1000 is configured to eject at least one flow adjusting gas1020 to adjust a trajectory of the hydrogen 1030 away from the mask toreduce hydrogen permeation at the edge 950 of the reticle (mask) 250.The ability of at least one flow adjusting gas 1020 forcing thetrajectory of the hydrogen 1030 away from the reticle reducing thehydrogen permeation at the edge 950 of the reticle 250 is directlyproportional to a molecular weight (density, if pressurized) of the atleast one flow adjusting gas 1020. In some embodiments, the at least oneflow adjusting gas includes a purging gas such as, for example, helium(He), neon (Ne), argon (Ar). In some embodiments, the at least one flowadjusting gas is determined based on the molecular weight (density) by acombination of purging gases depending on the trajectory of the hydrogen1030. As the molecular weight of the at least one flow adjusting gas1020 is greater than molecular weight of the hydrogen flow 930, usingthe at least one flow adjusting gas 1020 with a high molecular weight(density) may affect the process or other components disposed in theexposure chamber 205. Thus, the molecular weight (density) of the atleast one flow adjusting gas 1020 (or output pressure of the correctingnozzle 1010) is determined, in some embodiments, to be no higher thanwhat is necessary to reduce the hydrogen permeation.

FIG. 5C illustrates a plurality of nozzles and a plurality of exhaustnozzles according to embodiments of the disclosure. As shown in FIG. 5C,in some embodiments, the correcting nozzle 1010 includes a plurality ofnozzles 1012 arranged in the X direction. In other embodiments, thecorrecting nozzle 1010 is a slit shape nozzle 1014 having a smallerwidth in the Z direction than in the X direction. A distance dl in the Zdirection between the Y-nozzle for hydrogen 1016 and the correctingnozzle 1010 (center-to-center distance) is in a range from about 1 mm toabout 20 mm.

In some embodiments, the trajectory correcting assembly 1000 furtherincludes an exhaust nozzle 1070 to adjust the trajectory of the hydrogenaway from the mask thereby reducing hydrogen permeation at the edge ofthe reticle (mask).

FIGS. 5D and 5E are schematic views of trajectory of the hydrogen andthe exhaust nozzle 1070 according to embodiments of the disclosure. Asshown in FIG. 5D, the exhaust nozzle 1070 is configured to adjust thetrajectory of the hydrogen 1030 by forcibly exhausting the hydrogen 930away from the reticle, thereby reducing the hydrogen permeation at theedge 950 of the reticle 250. In some embodiments, the exhaust nozzle1070 is connected to the vacuum and/or pumping assembly 1080. As shownin FIG. 5E, the ability of the exhaust nozzle 1070 forcing thetrajectory of the hydrogen 1030 away from the edge 950 of the reticle250 is proportional to the exhaust pressure, which is controlled andadjusted by the controller 1410. For example, as shown in FIG. 5D, theexhaust nozzle 1070 and the Y-nozzle 920 are located at the samelevel/distance away from the bottom surface of the reticle 250. In someembodiments, as shown in FIG. 5E, the exhaust nozzle 1070 may be locatedat a greater distance than the Y-nozzle 920 further away from the bottomsurface of the reticle 250 to adjust the trajectory of the hydrogen 1030by forcibly exhausting the hydrogen 930 away from the reticle. In someembodiments, the exhaust nozzle 1070 is configured to adjust thetrajectory of the hydrogen in combination with the correcting nozzle1010 adjacent to the Y-nozzle for hydrogen 1016.

As shown in FIG. 5F, in some embodiments, the exhaust nozzle 1070includes a plurality of exhaust nozzles 1080. In some embodiments, theplurality of exhaust nozzles 1080 are arranged within an exhaust slit1090. In some embodiments, the exhaust nozzle 1070 is configured toadjust a direction of the plurality of nozzles 1080 of the correctingnozzle arranged in the exhaust slit 1090 to adjust the flow of thehydrogen. In some embodiments, the plurality of exhaust nozzles 1080 areconfigured to adjust the trajectory of the hydrogen in combination withthe correcting nozzle 1010.

FIG. 6 shows an exemplary schematic view of an apparatus for reducinghydrogen permeation of the mask according to some embodiments of thepresent disclosure. In some embodiments, the corrected trajectory of thehydrogen using the at least one flow adjusting gas 1020 is measured by agas flow detector 1050. In some embodiments, a variation in hydrogenflow corrected by the at least one flow adjusting gas 1020 is used as afeedback 1007 to a controller 1410 for adjusting a gas pressure from thecorrecting nozzle 1010. In some embodiments, the trajectory correctingassembly 1000 includes a plurality of purging gas including, forexample, helium (He), neon (Ne), argon (Ar), deuterium (D₂) and/ornitrogen (N₂), and measures the variation in hydrogen flow corrected bythe correcting nozzle 1010. The signal from the gas flow detector 1050is used as a feedback for adjusting the gas pressure from the correctingnozzle 1010 in some embodiments. In some embodiments, the feedback maybe connected with a gas mixer 905 to mix two or more of the at least oneflow adjusting gas 1020 to adjust the hydrogen flow path below the maskbased on a molecular weight. In some embodiments, the trajectorycorrecting assembly 1000 further includes a gas flow rate controller 915configured to adjust the trajectory of the hydrogen away from the mask.

The feedback mechanism provided in some embodiments may further send anotification based on a hydrogen flow measurement information indicatingthe hydrogen flow measurement is within the acceptable hydrogen flowmeasurement range. In some embodiments, the notification includes acorrected hydrogen flow from the hydrogen nozzle using the correctingnozzle 1010. In some embodiments, the notification also includes a gaspressure of the one or more of the at least one flow adjusting gas 1020.In some embodiments, the notification also includes an angle of thecorrecting nozzle 1010 coupled to the reticle mini environment (RME 940shown in FIG. 4B) adjacent to the reticle, in which the angle is betweenthe correcting nozzle 1010 and the surface the reticle. In someembodiments, based on the generating the notification, the feedbackfurther sends the notification to a first external device associatedwith the gas flow rate controller 915 and a second external deviceassociated with a gas pressure controller.

In some embodiments, gas flows of the hydrogen and at least one flowadjusting gas are monitored by an airflow pattern recognition system1500 (shown in FIGS. 7B and 7C) using one or more imaging orvisualization techniques. Various air flow patterns with various gasflow conditions (gas kind, flow rate, gas speed, pressure, temperature,etc) are corrected and accumulated in a storage (memory) as gas flowpattern data. In some embodiments, hydrogen accumulation patterns arealso obtained and stored. In some embodiments, correlations between oneor more parameters of the gas flow conditions of the hydrogen gas andcorrecting gas are analyzed and obtained by using analytical methods,such as a machine learning method. In some embodiments, the gas flowpattern data are obtained before an EUV lithography operation for theactual wafer manufacturing process is performed. During the EUVlithography operation, the gas flow patterns of the hydrogen gas and theflow adjusting gas are monitored, and then compared with the accumulatedgas flow pattern data. Based on the comparison, one or more of the gasflow parameters for the hydrogen gas and/or the correcting gas isadjusted.

FIG. 7A illustrates a collect-analyze-tune (CAT) operation 900 inaccordance with some embodiments of the present disclosure. The CAToperation starts with collecting Y-nozzle airflow data measured by a gasflow detector, in operation S910. Then, in operation S920, the Y-nozzleairflow data is analyzed. Finally, in operation S930, Y-nozzle airflowis tuned based on the Y-nozzle airflow analysis. When analyzing theY-nozzle airflow data, the trajectory correcting assembly 1000 usesvarious pattern recognition techniques such as machine learning, bigdata mining, and neural network.

FIGS. 7B and 7C illustrate block diagrams of non-limiting examples of anairflow pattern recognition system 1500 in accordance with one or moreembodiments described herein. As shown in FIG. 7B, the airflow patternrecognition system 1500 includes a hydrogen airflow variable component1502 that receives an update 1504. The update 1504 includes a change orupdate to one or more parameters of the gas flow conditions associatedwith the hydrogen and the correcting gas, such as gas kind, flow rate,gas speed, pressure, and temperature, received from the controller 1410.In some embodiments, the controller 1410 is configured to update controlvariables to remove or mitigate a hydrogen permeation or vulnerabilitythat was detected by the hydrogen airflow analysis to incorporate newcorrecting actions/elements 1590. In some embodiments, the update 1504can be received from another suitable controller or database. Inresponse to the update 1504, the hydrogen airflow variable component1502 is configured to generate variable vector data 1506. The variablevector data 1506 mathematically represents the hydrogen airflow variablecomponent 1502 mathematically, such as by a mathematical model.

The machine learning component 1512 is configured to receive thevariable vector data 1506 from the hydrogen airflow variable component1502, and employ a classifier algorithm 1514 (or another suitableclassifier or machine learning technique) to identify an affectedportion 1516. The affected portion 1516 includes a subset of amathematical model that is affected by the update 1504. In someembodiments, the classifier algorithm 1514 and/or machine learningcomponent 1512 can mark or tag the affected portion 1516 with a severityof the affected portion.

In some embodiments, the classifier algorithm 1514 is trained inadvance. For example, the gas flow pattern data may be obtained andtrained before the EUV lithography operation for the actual wafermanufacturing process is performed. Based on the training, theclassifier algorithm 1514 is configured to learn how a particularvariable (e.g., molecular weight) affects the mathematical model 1508and/or how to adjust/remedy a trajectory in the context of mathematicalmodel 1508. In some embodiments, the machine learning component 1512 isconfigured to identify the affected portion 1516 based on the variablevector data 1506.

The trajectory analysis component 1518 is configured to receive theaffected portion 1516 or related information. The trajectory analysiscomponent 1518 conducts a correcting gas airflow analysis 1582 based onthe affected portion 1516. For example, the trajectory analysiscomponent 1518 combines the correcting gas airflow analysis 1582 and thehydrogen airflow variable component 1502 on the mathematical model 1508and determines a correcting action 1590 by machine learning techniques(e.g., classifier algorithm 1514) and represented by the affectedportion 1516. In other words, based on machine learning, in someembodiments, the trajectory analysis component 1518 identifies theextent of the updates to mathematical model 1508 and how such updatescan be provided.

In some embodiments, the trajectory analysis component 1518 isconfigured to generate one or more correcting actions. The correctingaction 1590 represents a newly generated mathematical model 1508 thatcan be employed to remedy the affected portion 1516. By applying thecorrecting gas airflow analysis based on the hydrogen airflow analysis,a feedback is provided in real-time to generate a mathematical model1508.

As shown in FIG. 7C, the airflow pattern recognition system 1500includes the correcting gas airflow analysis component 1582 and themachine learning component 1512. The correcting gas airflow analysiscomponent 1582 receives parameters P1 through PN (1502 ₁-1502 _(N)) andupdated parameters P′1 through P′N (1504 ₁-1504 _(N)), where N is anypositive integer. In some embodiments, the correcting gas airflowanalysis component 1582 generates mathematical models M1 through MN(models 1506 ₁-1506 _(N)) and M′1 through M′N (models 1508 ₁-1508 _(N))based on the received parameters 1502 ₁-1502 _(N) and the updatedparameters 1504 ₁-1504 _(N), respectively, and send them to the machinelearning component 1512.

In some embodiments, the machine learning component 1512 compares M1 andM′1 to identify how the model changes based on specific updates 1532₁-1532 _(N). The hydrogen airflow variable component 1502 generates avariable vector data 1534 ₁-1534 _(N) in view of the specific update1532 ₁-1532 _(N) to identify how the particular variables of variablevector data 1534 ₁ affect M′1 relative to M1. In response, the machinelearning component 1512 updates the classifier algorithm 1514 byconducting a training 1510. Accordingly, the machine learning component1512 can identify how models (e.g., M1, MN, etc.) change relative tocertain updates 1532 and how those models will change according tocertain variables that are derived from the updates 1532 by hydrogenairflow variable component 1502. As a result, in some embodiments, theclassifier algorithm 1514 is trained to learn the consequences of thecorrecting gas airflow analysis component 1582 based on the variables ofthe parameters P1 through PN (1502 ₁-1502 _(N)).

FIG. 8 shows a flow chart of a method of controlling a feedback systemof an extreme ultraviolet (EUV) radiation source according to anembodiment of the disclosure. The method includes, at S1010, providing areticle on a reticle holder. At S1020, hydrogen gas is ejected towardsthe reticle. The trajectory correcting assembly includes a correctingnozzle and a gas flow detector. The correcting nozzle is configured todispense at least one flow adjusting gas to adjust a trajectory ofhydrogen away from the mask to reduce hydrogen permeation at an edge ofthe mask, and the gas flow detector is configured to measure a variationof an airflow of the hydrogen adjusted by the at least one flowadjusting gas. Then, at S1030, the at least one flow adjusting gas isejected through the correcting nozzle to adjust a trajectory of hydrogenaway from the mask. At S1040, a hydrogen flow measurement is performedby the gas flow detector of a variation in hydrogen flow adjusted by theat least one flow adjusting gas. Consequently, at S1050, it isdetermined whether a variation in hydrogen flow measurement is within anacceptable range. Finally, at 51060, in response to a variation inhydrogen flow measurement that is not within the acceptable range ofvariation in hydrogen flow measurement, a configurable parameter of thetrajectory correcting assembly is automatically adjusted to set thevariation in hydrogen flow measurement within the acceptable range.

FIGS. 9A and 9B illustrate a configuration of the controller 1410 inaccordance with some embodiments of the disclosure. In some embodiments,a computer system 2000 is used as the controller 1410. In someembodiments, the computer system 2000 performs the functions of thecontroller as set forth above.

FIG. 9A is a schematic view of a computer system. All of or a part ofthe processes, methods and/or operations of the foregoing embodimentscan be realized using computer hardware and computer programs executedthereon. In FIG. 9A, a computer system 2000 is provided with a computer2001 including an optical disk read only memory (e.g., CD-ROM orDVD-ROM) drive 2005 and a magnetic disk drive 2006, a keyboard 2002, amouse 2003, and a monitor 2004.

FIG. 9B is a diagram showing an internal configuration of the computersystem 2000. In FIG. 9B, the computer 2001 is provided with, in additionto the optical disk drive 2005 and the magnetic disk drive 2006, one ormore processors, such as a micro processing unit (MPU) 2011, a ROM 2012in which a program such as a boot up program is stored, a random accessmemory (RAM) 2013 that is connected to the MPU 2011 and in which acommand of an application program is temporarily stored and a temporarystorage area is provided, a hard disk 2014 in which an applicationprogram, a system program, and data are stored, and a bus 2015 thatconnects the MPU 2011, the ROM 2012, and the like. Note that thecomputer 2001 may include a network card (not shown) for providing aconnection to a LAN.

The program for causing the computer system 2000 to execute thefunctions of an apparatus for controlling the apparatus in the foregoingembodiments may be stored in an optical disk 2021 or a magnetic disk2022, which are inserted into the optical disk drive 2005 or themagnetic disk drive 2006, and transmitted to the hard disk 2014.Alternatively, the program may be transmitted via a network (not shown)to the computer 2001 and stored in the hard disk 2014. At the time ofexecution, the program is loaded into the RAM 2013. The program may beloaded from the optical disk 2021 or the magnetic disk 2022, or directlyfrom a network. The program does not necessarily have to include, forexample, an operating system (OS) or a third party program to cause thecomputer 2001 to execute the functions of the controller 1410 in theforegoing embodiments. The program may only include a command portion tocall an appropriate function (module) in a controlled mode and obtaindesired results.

In various embodiments, a correcting nozzle is provided to adjust atrajectory of the hydrogen away from the mask. Such correction preventshydrogen permeation at the edge of the reticle (mask), therebyincreasing the lifetime of the reticle and increasing the throughput ofthe EUV lithography system as well as reducing the cost of maintenanceof the reticle.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

An embodiment of the disclosure is an apparatus for reducing hydrogenpermeation of an extreme ultraviolet (EUV) mask. The apparatus includesa mask stage configured to hold the mask, a hydrogen dispensing nozzleconfigured to eject hydrogen below the mask, and a trajectory correctingassembly. The trajectory correcting assembly includes a correctingnozzle disposed between the mask stage and the hydrogen dispensingnozzle. The correcting nozzle is configured to dispense at least oneflow adjusting gas different from hydrogen to adjust a trajectory of thehydrogen away from the mask to reduce hydrogen permeation at an edge ofthe mask.

In some embodiments, the apparatus further includes a gas flow detectorconfigured to measure a variation of a flow of the hydrogen adjusted bythe at least one flow adjusting gas. In some embodiments, the apparatusfurther includes a gas mixer configured to mix two or more of flowadjusting gases. In some embodiments, the apparatus further includes agas flow rate controller configured to adjust the trajectory of thehydrogen away from the mask. In some embodiments, the apparatus furtherincludes a plurality of exhaust nozzles configured to forcibly exhaustthe hydrogen away from the mask. In some embodiments, the correctingnozzle includes a plurality of nozzles arranged in a slit.

Another embodiment of the disclosure is a method of manufacturing asemiconductor device. The method includes providing a reticle on areticle holder. Hydrogen flows over the reticle and reticle holder.Then, a trajectory correcting assembly is provided that includes acorrecting nozzle and a gas flow detector. The correcting nozzle isconfigured to dispense at least one flow adjusting gas to adjust atrajectory of the hydrogen away from the reticle to reduce hydrogenpermeation at an edge of the reticle. The gas flow detector isconfigured to measure a variation of a flow of the hydrogen adjusted bythe at least one flow adjusting gas. Subsequently, the at least one flowadjusting gas flows through the correcting nozzle to adjust a trajectoryof hydrogen away from the reticle.

In some embodiments, Flows of the hydrogen and the at least one flowadjusting gas are then monitored. An then, the flow of the at least oneflow adjusting gas is adjusted based on monitored results of thehydrogen and the at least one flow adjusting gas. In some embodiments, ahydrogen flow measurement is performed by the gas flow detector of avariation in hydrogen flow adjusted by the at least one flow adjustinggas. Then, it is determined whether a variation in hydrogen flowmeasurement is within an acceptable range. In response to a variation inhydrogen flow measurement that is not within the acceptable range ofvariation in hydrogen flow measurement, a configurable parameter of thetrajectory correcting assembly is automatically adjusted to set thevariation in hydrogen flow measurement within the acceptable range. Insome embodiments, a pressure of a plurality of exhaust nozzlesconfigured is adjusted to forcibly exhaust the hydrogen away from thereticle. In some embodiments, a direction of a plurality of nozzles ofthe correcting nozzle arranged in a slit is adjusted to adjust the flowof the hydrogen. In some embodiments, a flow rate of a gas flow ratecontroller is adjusted, in which the gas flow rate controller isconfigured to adjust the trajectory of the hydrogen away from thereticle. In some embodiments, a distance between a Y-nozzle for hydrogenand the correcting nozzle is adjusted in a range from 1 mm to 20 mm toadjust the flow of the hydrogen.

Another aspect of the present disclosure is a method of manufacturing asemiconductor device. The method includes proving an extreme ultraviolet(EUV) lithography system that includes a mask stage configured to hold amask, a hydrogen dispensing nozzle configured to eject hydrogen belowthe mask, a trajectory correcting assembly, and a controller. Thetrajectory correcting assembly includes a correcting nozzle configuredto dispense at least one flow adjusting gas to adjust a trajectory ofthe hydrogen away from the mask to reduce hydrogen permeation at an edgeof the mask, and a gas flow detector configured to measure a variationof a flow of the hydrogen adjusted by the at least one flow adjustinggas. The controller is coupled to the trajectory correcting assembly.The method then includes, using the controller, determining whether thevariation in hydrogen flow measurement at the gas flow detector iswithin an acceptable range. In response to a determination that thevariation in hydrogen flow measurement is not within an acceptablerange, the controller automatically adjusts a configurable parameter ofthe trajectory correcting assembly.

In some embodiments, a gas mixer is provided to mix two or more of flowadjusting gas based on a molecular weight. In some embodiments, thecontroller is configured to control the gas mixer to change thetrajectory of one of or both the hydrogen nozzle and at least one flowadjusting gas. In some embodiments, the controller is configured tocontrol an angle of the correcting nozzle with respect to a surface themask stage facing the correcting nozzle. In some embodiments, thecontroller adjusts a gas pressure of the at least one flow adjustinggas. In some embodiments, a plurality of exhaust nozzles are provided toforcibly exhaust the hydrogen away from the mask. In some embodiments,the controller is configured to send a notification including a gaspressure of the hydrogen and the at least one flow adjusting gas.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. An apparatus for reducing hydrogen permeation ofan extreme ultraviolet (EUV) mask, the apparatus comprising: a maskstage configured to hold the mask; a hydrogen dispensing nozzleconfigured to eject hydrogen below the mask; and a trajectory correctingassembly including a correcting nozzle disposed between the mask stageand the hydrogen dispensing nozzle, wherein the correcting nozzle isconfigured to dispense at least one flow adjusting gas different fromhydrogen to adjust a trajectory of the hydrogen away from the mask bycontacting a flow the hydrogen to reduce hydrogen permeation to themask.
 2. The apparatus of claim 1, further comprising a gas flowdetector configured to measure a variation of a flow of the hydrogenadjusted by the at least one flow adjusting gas.
 3. The apparatus ofclaim 1, further comprising a gas mixer configured to mix two or more offlow adjusting gases.
 4. The apparatus of claim 1, further comprising agas flow rate controller configured to adjust the trajectory of thehydrogen away from the mask.
 5. The apparatus of claim 1, furthercomprising a plurality of exhaust nozzles configured to forcibly exhaustthe hydrogen away from the mask.
 6. The apparatus of claim 1, whereinthe correcting nozzle includes a plurality of nozzles arranged in aslit.
 7. A method of manufacturing a semiconductor device, the methodcomprising: providing a reticle on a reticle holder; flowing hydrogenover the reticle and reticle holder; providing a trajectory correctingassembly, wherein the trajectory correcting assembly includes: acorrecting nozzle configured to dispense at least one flow adjusting gasdifferent from hydrogen to adjust a trajectory of the hydrogen away fromthe reticle to reduce hydrogen permeation to the reticle; and a gas flowdetector configured to measure a variation of a flow of the hydrogenadjusted by the at least one flow adjusting gas; and flowing the atleast one flow adjusting gas through the correcting nozzle to adjust atrajectory of hydrogen away from the reticle by contacting the flow ofthe hydrogen.
 8. The method according to claim 7, further including:monitoring flows of the hydrogen and the at least one flow adjustinggas; and adjusting the flow of the at least one flow adjusting gas basedon monitored results of the hydrogen and the at least one flow adjustinggas.
 9. The method according to claim 7, further including: performing ahydrogen flow measurement by the gas flow detector of a variation inhydrogen flow adjusted by the at least one flow adjusting gas;determining whether a variation in hydrogen flow measurement is withinan acceptable range; and in response to a variation in hydrogen flowmeasurement that is not within the acceptable range of variation inhydrogen flow measurement, automatically adjusting a configurableparameter of the trajectory correcting assembly to set the variation inhydrogen flow measurement within the acceptable range.
 10. The methodaccording to claim 9, further including: adjusting a pressure of aplurality of exhaust nozzles configured to forcibly exhaust the hydrogenaway from the reticle.
 11. The method according to claim 9, furtherincluding: adjusting a direction of a plurality of nozzles of thecorrecting nozzle arranged in a slit to adjust the flow of the hydrogen.12. The method according to claim 9, further including: adjusting a flowrate of a gas flow rate controller configured to adjust the trajectoryof the hydrogen away from the reticle.
 13. The method of claim 9,further comprising: adjusting a distance between a Y-nozzle for hydrogenand the correcting nozzle in a range from 1 mm to 20 mm to adjust theflow of the hydrogen.
 14. A method of manufacturing a semiconductordevice, the method comprising: providing extreme ultraviolet (EUV)lithography system, wherein the EUV lithography system includes: a maskstage configured to hold a mask; a hydrogen dispensing nozzle configuredto eject hydrogen below the mask; a trajectory correcting assemblyincluding: a correcting nozzle configured to dispense at least one flowadjusting gas to adjust a trajectory of the hydrogen away from the maskto reduce hydrogen permeation at an edge of the mask; and a gas flowdetector configured to measure a variation of a flow of the hydrogenadjusted by the at least one flow adjusting gas; and a controllercoupled to the trajectory correcting assembly, determining, by thecontroller, whether the variation in hydrogen flow measurement at thegas flow detector is within an acceptable range, and adjusting, by thecontroller, in response to a determination that the variation inhydrogen flow measurement is not within an acceptable range, aconfigurable parameter of the trajectory correcting assembly.
 15. Themethod of claim 14, further including: providing a gas mixer configuredto mix two or more of flow adjusting gas based on a molecular weight.16. The method of claim 15, wherein the controller is configured tocontrol the gas mixer to change the trajectory of one of or both thehydrogen nozzle and at least one flow adjusting gas.
 17. The method ofclaim 14, wherein the controller is configured to control an angle ofthe correcting nozzle with respect to a surface of the mask stage facingthe correcting nozzle.
 18. The method of claim 14, further including:adjusting, by the controller, a gas pressure of the at least one flowadjusting gas.
 19. The method of claim 14, further including: proving aplurality of exhaust nozzles configured to forcibly exhaust the hydrogenaway from the mask.
 20. The method of claim 14, wherein the controlleris configured to send a notification including a gas pressure of thehydrogen and the at least one flow adjusting gas.